In many fields, it is often necessary to measure the amount that a vertical surface or frame has been bent or deflected. Such a situation arises in disaster recovery in response to wind damage or other accidents or natural disasters. Measurement of damage is necessitated by retrofit procedures which may be required as well as insurance recovery and insurance adjustment.
One of the major problems in measuring the deflection over longs spans, such as in large window frames, is the lack of convenient, portable tools to measure the deflection. A typical tool available is a masons bubble level as well known in the art. A bubble level determines whether a surface is level and plumb (truly vertical or horizontal), but does not quantify the deflection of the surface.
U.S. Pat. No. 5,388,338 to Majors discloses an expandable screed level. The level has an open rectangular cross section and uses liquid bubble levels to determine slope. The device is expandable by adding additional sections at either end. The additional sections attach by means of a smaller rectangular cross section that fits inside the main body. The additional sections are retained in position by use of a latching mechanism. However, Majors makes no provision for measuring the displacement of a warp in a frame.
U.S. Pat. No. 5,433,011 to Scarborough et al discloses an expandable level. The level is expandable as a straight level, a square, a T-square and other shapes. Additional sections are added to the main body through a tongue and groove arrangement. A pressure screw is tightened to lock the pieces together. The device measures slope through use of liquid bubble levels. Each expansion piece contains at least one level. However, no provision for measuring deflection of a frame is provided.
U.S. Pat. No. 4,939,848 to Armstrong discloses an improved alignment gauge to check misalignment of the body of a vehicle. The device determines the distance between various physical points on the vehicle in order to aid in proper alignment. The device consists of a needle indicator attached at one end of a beam. The beam supports a horizontal and vertical liquid bubble level. The invention produces a precise result, but does not address the problems of ease of transport and use. It does not measure deflection along a long linear surface, but rather at specific points.
U.S. Pat. No. 7,497,022 to Aarhus discusses an extendable level. Telescopic extensions are contained within a main body of the level extension. Each terminates in an end piece. The extensions are supported by cross members. Each cross member and the main body includes a liquid bubble level. The invention facilitates viewing but does not measure depth or deflection.
US 2003/0033722 to Lanham discloses a telescopic leveling instrument having a body and telescopic extensions. The telescopic extensions are oriented horizontally or vertically. The extensions are marked to allow distance measurement. The main body includes a bubble level. The device measures distance but does not measure depth or deflection perpendicular to the surface.
U.S. Pat. No. 5,303,480 to Chek discloses a device to measure the amount of deviation of a patient's facial symmetry from a “standardized norm.” The device consists of a rod shaped base and a portable probe that is movable horizontally. The base is placed against a patient's sternum and maintained at horizontal by monitoring a liquid bubble level. The probe is then set against various facial features and the horizontal and radial distance from the sternum to the probe is measured. However, the device does not provide a means to measure depth between two points on a particular surface or over long distances. Further, the device is incapable of measuring multiple points of deflection at the same time.
U.S. Pat. No. 4,691,443 to Hamilton et al discloses a vehicle alignment system. The system includes fittings connected to beams that allow access to a vehicle, while maintaining the measurement surfaces in horizontal or vertical orientation. Lasers are used to project X, Y and Z coordinates. The device is not portable. The device also does not provide a means to measure deflection of a freestanding vertical beam.
U.S. Pat. No. 5,388,338 to Majors describes an extendable screed level. The level includes extensions that mount to a main body. The extensions enter a channel in the main body and are locked into position with releasable catches. The extensions produce an increase in length that allows the level to span retaining walls of various widths, forming a barrier to hold wet cement. The level of Majors includes a bubble level to ensure the surface of the wet cement is horizontal. However, Majors does not provide for determining a measurement of deflection of vertical surfaces.
Additionally, prior art does not address the problem in measuring deflection in a vertical beam by a single individual. Often the window frames are quite large, requiring spanning eight or more feet in order to determine the deflection. It is difficult and unwieldy for a single individual to hold prior art levels against such a window frame and measure the deflection accurately or consistently.
Therefore, a need exists for an economical device for measuring deflection of large surfaces, including window frames, which can be operated single-handedly. A need also exists for a deflection measurement device which is portable and may be used in the field. Still further, a need exists for a simple uncomplicated device to measure deflection of a vertical beam at or around its center point. A further need exists for a device which is expandable to fit both large and small spans, without the need for additional tooling or calibration. A still further need exists for a device to measure many points of deflection over a surface simultaneously between a pair of reference points.